The present invention relates to a camera lifting apparatus equipped with a camera unit for picking up the image of a work area of a cargo carrying apparatus, such as forks, at the time of doing a cargo carrying work in a high position and a cargo handling operation aiding apparatus in an industrial vehicle equipped with a carriage which is lifted up and down along a mast, such as, for example, a forklift.
For example, the vehicle body of a forklift which is an industrial vehicle is equipped with a multi-level mast that lifts a carriage having an attachment, such as forks, up and down. At the time of performing load pickup or load deposition at a high place in a rack, a driver operates a lift lever to protract or retract the multi-level mast by hydraulic driving. Further, the driver moves the forks upward along the mast to position the forks to a predetermined position with respect to a shelf surface or a pallet on a rack (cargo handling lever operation).
At the time of the positioning work, the driver must manipulate the lift lever while checking with the eyes if the forks are positioned to holes in the pallet or slightly above the shelf surface by looking up at a high place (e.g., 3 to 6 meters). It is however extremely difficult to determine if the forks and a pallet or the like are horizontally positioned with the eyes by looking up at a high place from below, and even a skilled person needs time for this positioning. In case of moving the forks gradually closer to a load or a rack by manipulating the lift lever, for example, the work should be carried out carefully, thus lowering the working efficiency.
There is an apparatus known that has, for example, a camera attached to the carriage and allows the driver to see a picked up image of a rack or a pallet which is seen in front of the forks via the screen of a display device at the driver's seat in order to solve the above problem. This apparatus aids the positioning work of the forks at a high place.
In the conventional apparatus, the camera is fixed to the distal end portion or the side portion of the forks or a predetermined position of the mast. The place where the image of the work area can be picked up approximately from the front is desirable as the place for securing the camera. In case where the camera is fixed in the vicinity of the proximal end portion of the forks, while the image of the work area can be picked up widely at the time of load pickup, a load on the forks interferes at the time of load deposition, thus allowing image pickup of only a narrow work area around the shelf surface where the load is to be deposited. Therefore, the camera attaching position was limited to a place, such as the distal end portion of the forks or the side surface of the forks, where miniaturization of the camera would be required. The restriction of the camera attaching position might result in a case where the optimal aiding would be difficult.
To solve the above problem, U.S. Pat. No. 5,586,620, for example, discloses an apparatus which has a camera attached to the carriage of a forklift to allow a picked-up image of the state of a rack, a pallet or the like seen in front of the forks to be seen on the screen of a display device at the driver's seat, thereby supporting the work of positioning the forks at a high place. The camera can be lifted up and down with respect to the carriage via a lifting mechanism. Further, the camera is attached to the carriage in such a way as to be urged downward by a spring. When the carriage moves down near to a lowest lift-down position, the camera abuts on a plate provided on the mast so that the camera moves upward against the urging force of the spring and is stored in a protection position. When the forks moved upward by a predetermined distance from the lowest lift-down position, the camera moves down from the carriage to be able to pick up an image in front of the forks. When the forks are moved down, the camera moves upward before the forks reach the lowest lift-down position and is stored in the protection position. Therefore, the collision of the camera against the floor is avoided.
In the case of the apparatus described above, the camera was always projecting downward from the carriage at a height equal to or higher than a position where the camera would move downward from the protection position (a height above the lowest lift-down position of the forks by a predetermined distance). That is, the image pickup position of the camera was fixed to a position below the forks by a predetermined distance in a load pickup work as well as a load deposition work. The arrangement of the camera below the forks by a predetermined distance is for picking up an image near the front of the forks without being interfered with a load on the forks at the time of load deposition.
From the viewpoint of aiding the positioning of the forks, it is desirable to provide an image picked up from the same height as the insertion sections of the forks. At the time of load deposition with no load that blocks the image pickup of the camera lies on the forks, particularly, it is desirable to arrange the camera at the same height as the insertion sections of the forks.
In the above apparatus, when the forks are located at a high place, the camera is projecting downward. Therefore, the camera might interfere with objects around at the time of a cargo carrying work.
The greater the amount of projection and the frequency of projection (or the projecting time) of the camera from the carriage, the greater the frequency of occurrence of the interference of the camera with surrounding objects. According to the conventional apparatus, the camera is likely to be interfered with surrounding objects and image pickup should be carried out from a low angle below the forks in load pickup mode.
There may be case where the positions of the forks with respect to a target are recognized using an image recognition technique based on an image picked up by the camera and a voice announce or the like is made to position the forks to the target or the like. In this case, it is preferable that the image of a target, such as a pallet or a rack, should be picked up from the front. That is, it is desirable that a pallet be a target in load pickup mode and a rack be a target in load deposition mode. Because the camera in the apparatus described in the aforementioned publication was secured relatively to the forks, however, it was not possible to change the position of the camera in accordance with a target that would differ in the contents of work.
The publication described above also discloses the structure that moves a single camera to a plurality of positions and a technique that can switch a plurality of image pickup positions using two cameras.
However, the image pickup positions could not be switched by changing the positions of the cameras at arbitrary heights. In case where plural cameras are arranged, extra cameras are needed and control of display on the screen of the display device becomes complicated.